Re: To be honest ...
I'm not sure what's cause and what's effect, there.
The Democrats never expected there to be a primary in 2020. After the 2016 fiasco, there was no-one (serious) in the party who was remotely ready to step up and start their campaign - because they'd all assumed that Hillary, having won 2016, would coast to an automatic renomination in 2020.
The present contenders are a bunch of has-beens who feel it's now or never, and a couple of opportunists who are mostly interested in making names for themselves - putting down markers for 2024 or beyond, rather than seriously contesting this nomination. All of them, I think, are assuming they'll lose.
But then, so was Trump in 2016. Politics is a tricky business, elections even more so.